This invention relates to an open type disposable diaper for absorption and containment of body wastes.
Japanese Patent Application Disclosure Gazette (Kokai) No. Sho58-13704 describes a disposable diaper comprising a liquid-pervious topsheet, a liquid-impervious backsheet, a liquid-absorbent core disposed between these two sheets, and a pair of side flaps extending transversely outward from transversely opposite side edges of the absorbent core. The side flaps are provided with elastic members longitudinally extending along the respective side edges of the absorbent core between the topsheet and the backsheet and bonded with under tension between the topsheet and the backsheet. The side flaps are folded back toward the topsheet above an area of the absorbent core along a pair of folding lines which extend in parallel to each other longitudinally of the diaper along the side edges of the absorbent core, respectively, so that the side flaps may be placed upon the topsheet above the area of the absorbent core. Then, along a pair of folding lines which extend in parallel to each other transversely of the diaper and substantially trisect a longitudinal dimension of the diaper, the diaper is folded one upon another in three layers with the topsheet inside.
In the case of the diaper described in the Japanese Patent Application Disclosure Gazette (Kokai) No. Sho58-13704, the side flaps are apt to be formed with permanent folds along the respective folding lines as a long period elapses after the diaper was folded since the side flaps are held between sections of the folded basic structure of the diaper. Each of the elastic members secured to the side flaps should be inevitably stretched on the folding line by a length corresponding to a thickness of the diaper basic structure as the diaper is folded. Under a contractile force of the elastic member thus stretched, the topsheet as well as the absorbent core are apt to be creased. Furthermore, in order to unfold the diaper and to put it on a wearer's body, this diaper inconveniently requires two steps of operation, i.e., the diaper folded in three layers must be opened longitudinally of the diaper and then the side flaps having permanent folds must be open transversely of the diaper.